Dennis D. McCarthyDennis D. McCarthy

Elements Elements of of

PredictionPrediction

Why are we here?Why are we here?

IERS Working Group on PredictionsIERS Working Group on Predictions Definitive user requirementsDefinitive user requirements Comprehensive look at prediction methodsComprehensive look at prediction methods Comprehensive look at new data setsComprehensive look at new data sets IERS Technical Note describing current state-IERS Technical Note describing current state-

of-the-art EOP prediction including of-the-art EOP prediction including requirements, methods, and data set requirements, methods, and data set information contentinformation content

Workshop Goal: Workshop Goal: Provide specific recommendations to Provide specific recommendations to

improve current techniques/IERS Products improve current techniques/IERS Products

History of Earth Orientation History of Earth Orientation PredictionPrediction

USNO began USNO began publishing predictions publishing predictions weekly in April, 1979weekly in April, 1979

Originally designed to Originally designed to improve Doppler improve Doppler satellite geodesysatellite geodesy

Original goal was 0.03” Original goal was 0.03” thirty days in advancethirty days in advance

Accuracy

Predictions 10 day 20 day 40 dayPolar Coordinates 0.0029" 0.005 0.0090"UT1-UTC 0.00072s 0.00208s 0.00563sCelestial Pole 0.0002" 0.0002" 0.0002"

Accuracy in 2009

In the next 30 years…?

Predictions 10 day 20 day 40 dayPolar Coordinates 0.012" 0.016" 0.027"UT1-UTC 0.0017s 0.0032s 0.0065s

Accuracy in 1979

30 Years Later

Input Data

Combination of Observations AstronomicalAstronomical

VLBIVLBI GPSGPS SLR/LLRSLR/LLR DORISDORIS

MeteorologicalMeteorological Oceanographic?Oceanographic? Geophysical?Geophysical?

Forecasts MeteorologicalMeteorological OceanographicOceanographic??

Information

Astronomical

Meteorological

Oceanographic

Geophysical

Accuracy

Polar Coordinates 0.00008"UT1-UTC 0.000057sCelestial Pole 0.0001"

Accuracy in 2009

In the next 30 years…?

Polar Coordinates 0.0020"UT1-UTC 0.00022s

Accuracy in 1979

30 Years Later

Limiting FactorsLimiting Factors

Systematic ErrorsSystematic Errors System stabilitySystem stability

Data availabilityData availability LatencyLatency

Constraints built into the input dataConstraints built into the input data

FormatsFormats

The Quest for the Holy Grail

"The High Mysterious Call" from: Rolleston, T. W. Parsifal, or the Legend of the Holy Grail retold from Ancient Sources

The Future?The Future? Develop robust software to

Combine data at the observation level

Adapt to changing systems Accept new contributions Accept streaming input

observations Use geophysical data? Provide sub-daily EOPs Provide real time analysis Be interactive Maintain reference system

stability

The Beginning of the Quest McCarthy, D. D., 1981, “On the adoption of a terrestrial

reference frame,” Reference coordinate systems for earth dynamics; Proceedings of the Fifty-sixth IAU Colloquium, Warsaw, Poland, September 8-12, 1980.

McCarthy, D. D. and Babcock, A. K., 1985, “The U.S. Naval Observatory C.O.R.E. (Combined solution for the orientation of the Earth) solution during project MERIT,” in Earth rotation and the terrestrial reference frame, I. I. Mueller (ed.) .

What should IERS provide to users?

Develop Model

Algorithm

Information

As tronomical

Meteorolog ical

Oceanographic

Geophys ical

?Test

Implement Model• Plots• Daily values• Sub-daily values• Mathematical Formulas

• Annual Values

Collect Information• User needs• Research

• Available Knowledge• Collect and analyze new observations

Disseminate ProductsE-mail Bulletins

Stored data

What Should IERS Provide to What Should IERS Provide to Users?Users?

What do users want?What do users want? Survey questionnairesSurvey questionnaires Product usageProduct usage Interactive feedbackInteractive feedback

What will users want in the future?What will users want in the future? Prediction of UT1-UTC will be more Prediction of UT1-UTC will be more

important if leap second disappears in 2019important if leap second disappears in 2019 Who will be the users of the future?Who will be the users of the future? What systems will be developed that What systems will be developed that

require predictions?require predictions? Dissemination processes in the futureDissemination processes in the future

General Requirements

One unique set of IERS prediction products

Easily accessible User friendly Reliable Meets users’ needs for

Accuracy Update frequency Spacing Prediction interval Metadata

Collect InformationCollect Information

Prograde Annual Wobble

Prograde Semi-annual Wobble

Atmospheric Tides

Precession

NutationsFree Core Nutation

1 2-2 -1Frequency in the Terrestrial Reference Frame (cycles per day)

2 3-1 0 1

0

Frequency in the Celestial Reference Frame (cycles per day)

POLAR MOTIONPOLAR MOTION

NUTATIONNUTATION

Po

wer

Ch

an

dle

r W

ob

ble

Frequency

Pow

er

annual

semi -annualsouthern oscillation

quasi-biennial oscillation

40-50 -day oscillations

monthly

fortnightly

atmospheric tidesdecade fluctuations

(from core?)

atmospheric modes

solid Earth and ocean tides

0.1 year-1

0.2 year-1

1 year-1

0.1 month-1

Observational Information

Survey of suitable Survey of suitable observational dataobservational data AstronomicalAstronomical MeteorologicalMeteorological OceanographicOceanographic HydrologicalHydrological GeophysicalGeophysical

Assessments of Assessments of likely future likely future observational data observational data

Develop ModelDevelop Model

Depends on prediction Depends on prediction interval and nature of interval and nature of prediction productprediction product Prediction for next 5 days? 30 Prediction for next 5 days? 30

days? decade?days? decade? Product provided hourly? Product provided hourly?

daily? annually?daily? annually? Statistical / physical ?Statistical / physical ? QualitiesQualities

AccuracyAccuracy Stability over timeStability over time Compatible with data likely to Compatible with data likely to

be availablebe available

Develop ModelDevelop Model

Implement ModelImplement Model

Tables of dataTables of data Daily?Daily? Sub-daily?Sub-daily? Quarterly?Quarterly? Annually?Annually?

Mathematical models/formulas?Mathematical models/formulas? Rotation matrix elementsRotation matrix elements UpdatedUpdated

As data become available?As data become available? Hourly?Hourly? Daily?Daily?

Disseminate ProductsDisseminate Products

On-demandOn-demand E-mailE-mail Web siteWeb site BulletinsBulletins

The Future: Predictions about Predictions

Increasing demand for near real-time information

Improved observational data

Improved Earth Orientation Observations

Densified geodetic networks Improved analysis models Improved celestial reference

frameCIP

TIO

CIO

Earth Rotation Angle

The Future: Predictions about Predictions

Increasing demand for near real-time information

Improved observational data Increased geophysical input

Increased Geophysical Input

• Improved meteorological forecast datao Densified observational

networkso Longer forecast intervals

• Oceanographic data• Hydrological data• Additional geophysical

data?

The Future: Predictions about Predictions

Increasing demand for near real-time information

Improved observational data Increased geophysical input Near real-time observations

Near Real-time Observations

GNSS

VLBI

Geophysical

The Future: Predictions about Predictions

Increasing demand for near real-time information

Improved observational data Increased geophysical input Near real-time observations Changes to forecast model(s)

Changes to Forecast Model(s)

Adapt toAdapt to User needsUser needs Data accuracyData accuracy Data latencyData latency

Multiple models may be requiredMultiple models may be required

The Future: Predictions about Predictions

Increasing demand for near real-time information

Improved observational data Increased geophysical input Near real-time observations Changes to forecast model(s) Near real-time product updates Sub-daily spacing New Products

New Products

High quality with prediction intervals < few days Lesser quality for prediction intervals < 2 weeks Low quality quarterly predictions for special users Interactive NTP UT1

Next StepsNext Steps Establish user needsEstablish user needs Support oceanographic dataSupport oceanographic data Develop models to meet user needs, data Develop models to meet user needs, data

accuracy and latencyaccuracy and latency

Let’s Get Started

Workshop Goal: Provide specific

recommendations to improve current techniques/IERS Products